Italian Sausage Burger With Garlicky Spinach

• 10 ounce baby spinach
• 2 tablespoon extra-virgin olive oil, plus more for brushing
• 2 cloves garlic, minced
• 1 teaspoon anchovy paste (optional)
• salt
• 1 pound sweet or hot italian sausages, casings removed
• 4 slices provolone cheese
• 1/4 cup sundried tomato pesto
• 4 ciabatta rolls, split and toasted

1. In a large skillet, bring ¼ inch of water to a boil. Add the spinach and cook, stirring, until just wilted, about 1 minute. Drain and press out as much water as possible. Wipe out the skillet.
2. In the same skillet, heat 2 tablespoons of olive oil until shimmering. Add the garlic and anchovy paste and cook over high heat, stirring occasionally, until fragrant, about 1 minute. Add the spinach, season with salt, and stir until just coated, about 10 seconds.
3. Light a grill or preheat a grill pan. Using slightly wet hands, form the sausage meat into four 4-inch patties, ¾-inch thick. Brush the burgers with oil and grill over moderate heat until browned and crusty on the bottom, about 5 minutes. Carefully flip the burgers. Top with cheese and grill until burgers are cooked through and the cheese is melted, about 5 minutes.
4. Spread the pesto on the rolls, and top with the burgers and spinach.